Grob 103 Twin Astir tailwheel axle?

We would like to replace the tail wheel on our Grob 103 Twin Astir. The bearing appears to be 25mm, but on each side there is an insert which reduces it down to a hole for a bolt which is 8mm. The inserts on both sides rotate separately, so I would not call it an axle, but if it were one piece it would be about 80mm long. I have been in contact with Wings & Wheels and they have the right wheel, but with the 25mm bearing hole empty. I don't see any obvious way to remove these inserts… no set screw, locking washer or anything. Do they just press in and need to be tapped out with some tool?

Here's a pictu https://docs.google.com/file/d/0B1pU...it?usp=sharing